High resolution electron beam lithography using ZEP-520 and KRS resists at low voltage

Abstract

A heavy ion implanted pocket 0.10 μm ntype metal-oxide-semiconductor field effect transistor with hybrid lithography (electronbeam/deep ultraviolet) and specific gate passivation process ZEP-520 and KRS resist systems have been evaluated as candidates for use in low voltage electron beam lithography. ZEP-520 is a conventional chain scission resist which has a positive tone for over two orders of magnitude in exposure dose. KRS is a chemically amplified resist which can be easily tone reversed with a sensitivity ϳ8 C/cm 2 at 1 keV. Both resist systems are shown to have sensitivities ϳ1 C/cm 2 for positive tone area exposures to 1 keV electrons. A decrease in contrast in 50 nm thick resist layers is seen when exposure voltage is lowered from 2 to 1 keV, indicating nonuniform energy deposition over the resist thickness. High resolution single pass lines have been transferred into both Si and SiO 2 substrates at both low and high voltages in each resist system without using multilayer resist masks. The ZEP-520 and KRS resists are shown to have resolutions of 50 and 60 nm, respectively, at 1 kV, within a factor of 2 of their high voltage resolutions under identical development conditions. A cusp shaped etch profile in Si allows high aspect ratio 20 nm wide trenches to be fabricated using these resists on bulk Si. Low voltage exposures have been used to pattern gratings with periods as small as 75 and 100 nm in ZEP-520 and KRS, respectively. Low voltage exposures on SiO 2 show no indications of pattern distortion due to charging or proximity effects.

A process study of electron beam nano-lithography and deep etching with an ICP system

“…The high sensitivity of ZEP520A reduces its exposure time by three times compared with that of PMMA [11,12] . The higher etch resistance allows us to transfer the ZEP520A resist pattern directly onto the substrate by dry etching.…”

Pyroelectric electron emission from −Z face polar surface of lithium niobate monodomain single crystal

“…Therefore the PD can only bear witness of plasma breakdown signature, which is manifested by an abrupt drop in the emission current. Also, we notice that the used E-beam-resist could show the current distribution only for a magnitude exceeding the sensitivity of 1μC/cm 2 for positive tone area exposures to 1 keV electrons [11]. The sensitivity is much larger than the total emitted charge density, ∼1nC/cm 2 , of CLN [2,12,17].…”

“…Receptive electron-beam-resist (ZEP-520, Nippon Zeon Co., Ltd.) was used to study the spatial distribution of the electron current. ZEP-520 E-beam-resist is known to have sensitivities of ∼1 μC/cm 2 for positive tone area exposures to 1 keV electrons [11]. It was very simple to use resist-coated wafers as detectors and the high sensitivity enabled us to observe current distribution of PEE.…”

PolyMethyl Methacrylate Thin-Film-Based Field Emission Microscope

“…A PMMA film has two interesting properties. First, a PMMA thin film acts as a positive resist when exposed to a low electron beam dose (5-20 μC/cm 2 for 1 keV beam) [7], but acts as a negative resist when it is exposed to a high dose (2000 μC/cm 2 for 1 keV beam) [7], [8]. Thus, it is possible to record the spatial distribution of an electron beam as well as distinguish a wide range of dose intensity.…”